On top of a rectangular card with sides of length and , an identical card is placed so that two of their diagonals line up, as shown in the figure (
). Continue the process, adding a third card to the second, and so on, lining up successive diagonals after rotating clockwise. In total, how many cards must be used until a vertex of a new card lands exactly on the vertex labeled in the figure?
3
4
5
6
No new vertex will land on B.
